Stationary guide vanes and rotating turbine blades in gas turbines often have internal cooling channels. Cooling effectiveness is important in order to minimize thermal stress on these airfoils. Cooling efficiency is important in order to minimize the volume of air diverted from the compressor for cooling.
Film cooling provides a film of cooling air on outer surfaces of an airfoil via holes in the airfoil outer surface from internal cooling channels. Film cooling can be inefficient because so many holes are needed that a high volume of cooling air is required. Thus, film cooling is used selectively in combination with other techniques.
Perforated cooling tubes may be inserted into span-wise channels in an airfoil to create impingement jets against the inner surfaces of the airfoil. A disadvantage is that heated post-impingement air moves along the inner surfaces of the airfoil and interferes with the impingement jets. Also, impingement tubes require a nearly straight airfoil for insertion, but some turbine airfoils have a curved span for aerodynamic efficiency.
Cooling channels may form an interconnected mesh that does not require impingement tube inserts, and can be formed in curved airfoils. The present invention improves efficiency and effectiveness in a cooling channel mesh.